Bracing is key in all athletic movement and sport. The plank forms the basis of this. Therefore, learn how and when to brace, perform movements with control and always progress to fluid movement e.g. ab wheel, hanging planks, rotational planks etc etc.The issue with the plank is if you just do the plank for your 'core' workout.
From a lower back rehab point of view, SOME clients who have low back pain can SOMETIMES brace too much, causing an actual increase in compression on certain structures, hence why some people in the fitness/health world are not such fans of the plank. If in doubt, see an expert regarding lower back pain and remember form is king.
